Berkheimer headed a project last year that brought adaptive bitrate streaming to the YouTube desktop player, enabling the player to automatically switch between different video quality settings based on your internet connection speed, among other factors.

Now he is bringing the same technology to mobile devices and TVs. “We are making it work just as it should,” Berkheimer told me during an interview this week.

From 240p to 4K

That may sound simple, but optimizing video playback has been a long journey for the Google-owned video site. Berkheimer joined YouTube six years ago, when there was just one default video quality — 320×240, also known as 240p. “That was really, really grainy video,” recalled Berkheimer.

Berkheimer joined YouTube when every video still looked grainy.

His team used Google’s cloud infrastructure to allow for additional codecs, bringing HD and eventually even 4k to the site. But with higher bitrates, buffering also became more of a problem.

The solution? Adaptive bitrate streaming, which is industry-speak for switching the quality of a video in midstream, without the need to re-buffer and start over. YouTube started switching from progressive downloads to adaptive bitrate streaming in its desktop player a year ago, and completed the process late last year.

The new player is keeping close eyes on the speed and health of your internet connection, explained Berkheimer: “It’s continuously monitoring the bandwidth and the throughput it is seeing,” he said, adding that it also keeps tabs on the size of your player. Are you watching a video in full screen? Then you can expect YouTube to send you more bits, as long as your connection is fast enough.

YouTube’s take on adaptive streaming

Adaptive streaming isn’t new: Companies like Netflix and Hulu have used the technology for some time to optimize their streaming experience. But YouTube had some unique challenges to solve when it rolled out its own implementation. For example, Netflix often starts with a lower-bitrate stream and then slowly scales up, which is why it can take a minute or so before full HD quality sets in.

That approach doesn’t really work for YouTube videos that only last a minute or two. YouTube tends to be more aggressive in sending out higher-quality video, and then scales down the video if necessary, Berkheimer explained. The site also makes use of the fact that you often watch more than one YouTube video in a row, and optimizes your bit rate across an entire session.

The results of these efforts have been encouraging. YouTube has seen buffering reduced by 20 percent since it launched adaptive streaming for its desktop player. That’s why the company is now taking the technology to TVs and mobile devices.

Next up: mobile and TVs

YouTube on TV: Buffering is much more noticeable on the big screen.

Of course, TVs require a lot more HD video, and buffering becomes even more obvious when you compare it to the nonstop experience of a traditional broadcast. Berkheimer told me that YouTube is working with the majority of the TV industry to bring adaptive streaming to TV sets, and that virtually all models introduced at CES this year already support the technology. The company is also working to bring adaptive streaming of YouTube videos to game consoles.

Mobile, on the other hand, comes with different challenges, as people move in and out of the reach of cell towers while they get their video fix on public transport.

And then there is this: “One of the biggest challenges we have is the global nature of YouTube,” said Berkheimer. Average mobile internet speeds are much slower in India and Brazil than in the U.S. and Europe, but videos still have to play without long and tiresome buffering. Broadband in Canada on the other hand is fast, but tightly rationed, with major ISPs charging their customers extra if they go over their caps.

That’s also one reason that those settings that allow you to manually change the bitrate of a YouTube video haven’t disappeared from the player yet — even though Berkheimer would very much like them gone. He told me that there have been some passionate discussions within the company about these manual settings. The result? For now, they’re staying.

But Berkheimer and his team are still working hard so that you can completely ignore them. “The most rewarding thing is that users don’t have to think about it,” he said.